Preparation of nitramines



United States Patent Ofioce 3,390,183 Patented J une 25, 1968 3,390,183PREPARATION OF NITRAMINES Milton B. Frankel, Menlo Park, and KarlKlager, Sacramento, Calif., assignors to Aerojet-General Corporation,Azusa, Calif., a corporation of Ohio No Drawing. Original applicationJune 8, 1964, Ser. No. 374,235. Divided and this application Dec. 27,1966, Ser. No. 620,200

6 Claims. (Cl. 260-583) This is a division of application Ser. No.374,235, filed June 8, 1964.

This invention relates to novel nitramides and to the conversion of thenitramides to nitramines.

The primary nitramines are a class of compounds having a wide variety ofuses, particularly in rocket propellants and explosives. The energyprovided by these compounds in a propellant or explosive composition isdependent to a considerable extent on the nitramine being present inessentially pure form. If the nitramine component in the composition iscontaminated or diluted with impurities or by-products from thesynthesis reactions, the overall effectiveness of the propellant orexplosive is reduced. Previously attempts have been made to prepareprimary nitramines by direct nitration of the free amine, or bydehydration of the nitrate salt. However, it has been found that primarynitramines, such as 3,6-dinitraza- 1,8-octane dinitramine, cannot beprepared in good yield by direct nitration of the corresponding amine orby dehydration of the nitrate salts of the corresponding primary aminebecause both of these techniques involve the contacting of the primarynitramine, as it is formed, with strong acid which causes excessivedecomposition of the desired product. This decomposition which occurs inthe prior art processes yields the primary nitramine in very impureform, making the compounds generally unsuitable ,for direct use inpropellants and explosives. Removal of these contaminants involves manyinvolved and costly purification procedures.

It has now been found that primary nitramines can be prepared from novelnitramides in good yield and without the need for contacting the primarynitramine with a strong acid. The primary nitramines of our inventionare directly obtained in high purity, thus avoiding elaborateafter-treatment and purification. According to'our invention, theprimary nitramines are obtained by preparing a nitramide by reaction ofthe corresponding amide with an ionic nitrating agent, followed byhydrolysis. This novel technique will be more fully understood, in bothits broad and specific aspects, from the discussion which follows. Itcan be seen, however, that by the practice of our invention, the contactof the ionic nitrating agent with the free primary amine is altogethereliminated.

It is an object of this invention to prepare primary nitramines withoutcontacting the primary nitramine with strong acid. It is still a furtherobject of this invention to prepare nitramines by a method which willprovide these compounds in better yield and greater purity than thosemethods previously known. Still another object of this invention is toprepare novel nitramides. These and other objects of this invention willbe apparent from the description which follows.

One of the starting materials in the preparation of the primarynitramines, according to the method of this invention, are thenitramides having the following general formula:

wherein A and A are alkylene radicals, preferably lower radical whereinR is as has already been defined.

The nitramides of the above formula are prepared by reacting (ReactionI) an ionic nitratingagent with a compound of the formula:

wherein A, A, R, R and n are as defined above. In the above reaction,the choice of the ionic nitrating agent is not critical. Any of thecommon strong ionic nitrating agents such as nitric acid, mixtures ofnitric acid and-sulfuric acid, mixtures of nitric acid and aceticanhydride, and mixtures of methyl nitrate and sulfuric acid may be used.Ionic nitrating agents containing nitric acid are preferred.

Generally speaking, a solvent is not required in order to prepare thenovel amides of our invention, according to Reaction I. However, ifdesired, any essentially inert solvent can be used, although carbontetrachloride is preferred. The proportions of the nitramine and ionicnitrating agent employed in the above reaction are not critical.Preferably the ionic nitrating agent is used in an amountstoichiometrically in excess to the amount of the nitramide employed soas to drive the reaction to completion within a reasonable length oftime. The reaction temperature may be varied over a wide range. Thepreferred range is from about l5 C. to about +35 C.

The novel nitramides prepared in the above manner are converted to thenitramines by hydrolyzing the nitramides in accordance with the generalreaction (Reaction II) set forth below.

amides undergo hydrolysis under basic conditions, such as by theaddition of sodium hydroxide, potassium hydroxide, ammonium hydroxide,and the like, to the amide. Optimum results were obtained when thehydrolysis was conducted in an ammoniacal media. It is to be understoodthat hydrolysis of the amide with base yields the amine in the form ofthe basic salt. The free amine is then obtained by neutralizing the saltwith a stoichiometn'c equivalent amount of an acid such as hydrochloricacid. In Reaction II, the reactants are ideally used instoichiometrically equivalent amounts since this results in the mostcomplete utilization of the reactants. However,

the proportions may be varied'over-a-wide range without adverselyaffecting the reaction.

The preparation of the nitramine is preferably carried"outbyfadditionfof the base'to the nitramide.-No solvents areordinarilyneces'sary; However, if desired, a polar solvent-suchaswater'may be -used."---:: Y f"- Itis desirable that'xth'ehydrolysis=-of the'nitramide be carried out at temperature between about0 C. and ai io't'1t' 100"" (3., althou' h this reaction range is notcritical to our 'invention. 11 Pressure '*n'otcritical in--the"preparation of the hitramid'e or the nitrami'ne'; Thereforethereactions may be run at any pressure, atmospheric pressure being mostconvenient.

The nitramides and nitramines of this invention are normally solids andmay be isolated in conventional manner by filtration, evaporation and/or crystallization.

To more clearly illustrate our invention, the following examples are:presentedlt is to be understood, however, that, these examples; areintended merely as illustrative embodiments of the. invention and shouldnot be construed as being limitative of the scope of said invention inany way. In the examples percentages are by weight unless otherwiseindicated.

Example I.--Prepar'ation ofN,N'-dinitro-3,6-dinitrazaoctamethylene-bis-acetamide To a 500 ml.flask, fitted with a mechanical stirrer, thermometer and droppingfunnel, was added 150 ml. of acetic anhydride. Keeping the temperatureof the mixture at 0 C. to 5 C., 150ml. of 100 percent nitric acid wasadded dropwise, and then*17.5' grams of 3,6dinitrazaoctamethylenebis-acetamide was added: The reaction mixture was stirred for 45 minutesat 0 C. to 5 C. and poured mice. The white solid which formed wascollected, washed with water and dried in vacuo over potassiumhydroxide. Recrystallization from ethylene dichloride gave 12.5 grams'(55.8 percent) of N,N'-dinitro-3,6

dinitraza-octamethylene-bis-acetamide, having a melting -point of 127?C. to 128 C. The elemental analysis of the product is as follows: 1

Calcd for C H N O percent: C, 29.27; H, 4.42; N, 27.31. Found, percent:C,-29.00; H, 4.25; N, 27.21. The 3,6- dinitraza-octamethylenebis-acetamide employed in the above example is prepared by the reactionof sodium inethoxide and acetic anhydride with 3,6-di-'nitr'aza-1,8-octane diamine hydrochloride, as is more fully disclosedin U.S. Patent No. 2,967,198, issued Jan. 3, 1961." i

- -Example II.- -Preparation ofN,-N'-dinitro-4-nitrazaheptamethylene-bis-caproamide To a flask is addedequal volumes of acetic anhydride and 100 percent nitric acid. Thetemperature is maintained at about 0-10" C. and4-nitraza-heptamethylen'ebis-caproamide is added to the mixed acids inincrements water, and dried,---2l .6 g. {44.5% -68-70.-'-"Recrystallization from carbomtetrachloride raised the melting pointto 7273.

Analysis.-Calcd for C H N O percent: C, 29.82;

H, 4.38. Found, percenttC, 29.93; H, 4.38.

V To 6.5 grams" f N,N'-dinitro 3,6-diriitraza-octamethyleiie-bi's-acetamide (pi epaired ace'ordingtoExainple I) was added 25 ml.of 28"percent ammonium hydroxide' 'I'he solid dissolved with theevolutionofheat. The solution was cooled in an ice bath and acidifiedwith dilute hydrochloric acid; The white solid which precipitated, wascollected, washed with water, and dried in vacuo over potassiumhydroxide. Recrystallization from. acetonechloroform gave- 5.1 grams(98.7%, based on the amide) of '3,6-,d initr aza-1,8-octane-dinitramine. in the form of .white needles, having amelting point of177-1'7 8".C. The elemental analysis of the product is as follows:

.iCalcdfor C l-1 N 0 percent: .C, 22.09; -H, 4.33; N, 34.35. Found,percent: C,'22.33; H,.4.28; N, 34.14. Example V. Prep'a'ration of'4-nitraza-l,7-

, heptan'e dinitramine To N,N-dinitr0-4 nitrazaheptamethylene-bis-caproamide (prepared as inExample II) is added anequivalent amount of 28 percent ammonium hydroxide. The solid is allowedto dissolve and is then acidified with dilute hydrochloric acid. -Thesolid precipitate is .collected, washed and dried to -give4nitraza?1,7-heptane dinitramine in goodyield. V

1 Example VI.Preparation of 3-nitraza-l,5-pentane 'dinitramine a To21.6. g. 10.067, mole) of N,N'- dinitro- 3-nitraza-per ttane-bis-acetar'nide was added ml. of water and 50 ml.

of concentrated ammonium hydroxide solution. The additionof the basecaused thesolid to dissolve with the evolution of heat. The solution waswarmed on the steambath for five minutes,,.cooled, and acidified withdilute hydrochloric acid. The white solid which precipitated wascollected, washed with water,-and dried, 15.0 g. (94%),

cording to the above examples. For example, 4.7-diniuntil the totaldiamine added is about stoichiometrically equivalent to the amount ofnitrating agent present. The mixture is agitated while being maintainedat about 5- 10 C. and then poured on ice. Recrystallization of theproduct in accordance with the procedure of Example I yieldsN,Nedinitro-4-nitraza-heptamethylene-bis-caproamide in the form of-rasolid product.

Example llL- -l reparation ofN,N'-dinitro-3-nitrazapentane-bis-acetamide In -a one-liter S-neckedflask,- fitted with a mechanical 4 at this temperature. To the acidsolution was added 35.0

g. (0.15 mole) of 3:nitrazapentane-bis-acetamide. After minutes at '-.-5to 0" the solid had dissolved. The solution was poured on ice, the whitesolid collected, washed with traza-decamethylene-bis-butyramide isnitrated with. a solution of methyl nitrate and sulfuricacid to formN,N'- dinitro 4,7-dinitraza-decamethylene-bis=butyramide. This lattercompound 'is then reacted sequentially with ammonium hydroxide andhydrochloric acid to form 4,7-dinitraza-l,l0 decane dinitramine. i

In the preparation of the nitramines and nitramides, according to themethod of this invention, it is sometimes desirable to agitate theingredients so as to assure more intimate contact and therebyv animpr'ovedrate of reactron. .I' ,,,The"nitramines and nitramides .of thisinvention contain a plurality jof nitro groups, and thus are inherentlyuseful as explosives-Thenitramide andnitramine compounds of ourlinvention will find utility in solid rocket propellants. Morespecifically, these compounds maybe used to increase the specificimpulse of the knownsolid pgopellants used in intermedi te andintercontinental ballistic missiles,'such as the aluminized polyurethanesysterns and those based on carbo'xy-terminatedpolybutadiene-azirindinyl curative binders.

The novel nitramides as well as the nitramines of this invention canalso be. used in any conventional explosive missile or rocket as the.T'main explosive charge. An example of such a missile is disclosed inUnited States Patent No. 2,470,162, issued May 17, 1949. The'highexplosives of this invention can be used in such a device by simplypacking the explosive in powdered form into the warhead of the missile.

This application is a continuation-in-part of applicants copending U.S.patent application, Ser. No. 209,276, filed July 9, 1962.

It will be understood that various modifications may be made in thisinvention without departing from the spirit or the scope of the appendedclaims.

with an ionic nitrating agent to form the nitramide of the formula:

wherein in each of the above formulae, R and R are lower alkyl radicals,A and A are lower alkylene radicals, and n is a small whole number offrom 1 to about 4; hydrolyzing the thus formed nitramide to thenitramine salt by the addition of a base, and neutralizing said salt tothe nitramine by the addition of a mineral acid.

2. The method of claim 1 wherein the hydrolysis is followed by theaddition of hydrochloric acid.

3. The method of claim 1 wherein the ionic nitrating agent containsnitric acid, and the hydrolysis is carried out by the addition ofammonium hydroxide.

4. The method of preparing 3-nitraza1,5-pentane dinitramine whichcomprises reacting 3-nitraza-pentane-bisacetamide with nitric acid,followed by hydrolysis with ammonium hydroxide and neutralization Withhydrochloric acid to form said dinitramine.

5. The method of preparing 3,6-dinitraza-1,8-octane dinitrarnine whichcomprises reacting 3,6-dinitraza-octamethylene-bis-acetamide with nitricacid, followed by hydrolysis with ammonium hydroxide and neutralizationwith hydrochloric acid to form said dinitramine.

6. The method of claim 5 wherein the reaction with the nitric acid iscarried out at a temperature of about 0 C. to about +10 C.

References Cited UNITED STATES PATENTS 10/1958 Sauer.

4/ 1961 Frankel et al.

OTHER REFERENCES CHARLES B. PARKER, Primary Examiner.

R. RAYMOND, Assistant Examiner.

1. THE METHOD OF PREPARING NITRAMINES OF THE FORMULA: